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I Patented June 4, 1935 UNITED STATES PATET OFFICE PRODUCING PATTERNS ON DARK COL- ORED SKINS OR, LEATHERS Hans Engels, Offenbach-on-the-Main, Germany,

assignor to firm Oswald Riigner, Offenbachon-the-Main, Germany No Drawing. Application July 16, 1931, Serial No. 551,287. In Germany July 19, 1930 3 Claims.

This invention relates to a process for the production of markings on naturally dark inexpensive skins or leathers, as well as to naturally dark skin or leather in which the natural pigment is wholly or partially destroyed or removed to form any suitably conceived marking which is in imitation of the natural markings of relatively expensive animal skins.

The invention concerns in particular a process for the production of the markings in question by bleaching the naturally dark pigment at localized areas by means of known reducing or oxidizing agents.

The invention is applicable to all kinds of fish, reptile and amphibian skins on which markings are to be produced and preferably to such skins which by nature are substantially of a uniform dark color. Fundamentally the use of the invention is independent of the condition of the skins to be treated, that is to say, it is independent of whether they are already tanned or treated chemically or mechanically in some other way, before the production of the markings is effected. It is therefore also possible to apply the invention to such naturally dark colored skins which have been dyed artificially. In this case the respective artificial dye is likewise wholly or partially destroyed or removed by the bleaching agent employed according to the invention.

Preference has for decades been given to high quality and expensive skins and more especially exotic reptile skins for the manufacture of footwear as well as for the production of articles common in the leather industry. The general use, however, of these sorts of leather more particularly in the shoe industry has up to about two to three years ago been curtailed principally because of the high prices since such skins or leathers for which there has been a particular demand due to their natural beautiful marking have proved too expensive for the manufacture of footwear on a larger scale. Consequently the aim of leather manufacturers has for some time been centered on the idea of producing artificially, imitations of these beautifully marked genuine skins. There is in addition also the growing interest in the possibility of producing any conceived marking on such skins or leathers in a simple and durable manner.

The method hitherto mainly consisted in approaching the genuine skins or leathers by appearance as closely as possible by printing markings of the desired kind and color on sheep, goat and similar skins. So far the result achieved has not been completely satisfactory. With the rising demand for genuine reptile skins such as for example the skins of lizards, snakes, crocodile and the like, experiments have also been made with cheap, relatively plain or entirely unmarked reptile skins or leather with the endeavour to ap- 5 proach as nearly as possible the expensive wellmarked skins or leathers by providing them with the requisite markings with a view to obtaining a cheaper product more suitable for large consumption. 10

The processes hitherto so far resorted to started without exception from the idea of bleaching the little or unmarked skins or leathers first of all as a Whole, that is to say, to remove as far as possible the natural pigment or color in order to obtain a relatively light mono-color leather. To the skins or leathers thus prepared a, more or less dark color has then been applied by means of printing rollers, stencils and similar technical expedients in order thus to attain the required marking on the light ground tone produced by bleaching. The result also by this method has hitherto been rather unsatisfactory throughout, inasmuch as the marking attained left much to be desired when compared with the genuine markings both as regards beauty and resemblance as well as durability.

With a View to obtaining a more perfect prod uct in this regard, use is made according to the invention of a process not so far employed for this purpose which is based on the principle of leaving completely unchanged the natural ground tone of the skin or leather in order that, above all, the effect, and the sound color properties of the natural genuine skin or leather will be retained. From the surface of the natural generally dark ground tone, the desired marking is then bleached out by means of a bleaching process hereinafter more fully described. According to the natural properties of the requisite skins or leathers the pigment at the respective points is entirely or partially destroyed or removed.

The chemical agents employed in this bleaching process have been known in the tanning industry for a long time. They have, however hitherto been used in a different manner than is the case with the process according to this invention. For example these bleaching agents have hitherto been used in strongly diluted solutions in the form of a bath in order not only to remove the natural marking of the skins or leathers as much as possible but also to impart to the whole skin or leather a substantially brighter color. For the purpose of this invention that process has been modified by utilizing the bleaching agents for the production of markings by means of rollers, stencils and the like. As already stated in some cases the existence of which the expert is able to gauge without difficulty, use may be made of suitable and likewise known reducing agents in place of oxidizing agents. It may, moreover, be left to the choice of the expert in what condition the bleaching agent employed is to be used, that is to say whether in a dissolved or undissolved state or in a pulverulent, paste-like or liquid form. It will be a matter also for the expert in particular circumstances to decide whether the production of the markings is to be efiected prior to or subsequent to the steeping or liming or soaking or pickling or dyeing of the requisite skins.

Some preferable examples of performing the invention for the production of markings by bleaching on skins or leathers which possess a natural more or less dark ground coloring are the following:

Example I (Reduction method) A fish skin as e. g. of a sea-wolf is steeped in the usual manner, limed and pickled and then treated with 1% sulphuric acid (0.25% concentration) and 7% common salt calculated on the weight of the raw or untreated skin. The skin thus prepared is then covered with a stencil perforated in accordance with the desired pattern or marking. By means of a fiat brush the openings in the stencil are brushed over with a concentrated solution of bleaching powder (about 1:1 mixture). The solution is allowed to act for about an hour and the excess bleaching powder is then removed. The further treatment of the skin takes place in the usual manner.

Example II (oxidizing process) A lizard skin of a substantially uniform dark natural color is in the usual manner steeped, limed and pickled and then treated with 1% sulphuric acid (0.25% concentration) and 7% common salt calculated for the weight of the raw skin. The skin thus prepared is covered with a stencil of the desired marking. Potassium permanganate dissolved in pasty condition is then brushed over the pattern in the stencil or the permanganate is applied thereto dry in powder form so as to fill up the openings. According to the intensity and thickness of the layer of the natural pigment of the skin treated the permanganate is allowed to act for a longer or shorter period, that is to say about 3 to 20 minutes. The skin thus treated is then subjected to the action of a 5% solution of sodium bisulphite until the areas thus treated with the bleaching agent have attained the desired light color. The skin is then rinsed and further treated in the usual manner.

Example III (Reduction method) The skin preliminarily treated as in the previous examples is covered with the stencil and the usual commercial 3% solution of hydrogen peroxide is sprayed on by means of a spraying nozzle, spraying gun or the like. In a similar manner use may be made also of a solution of potassium permanganate. In order that the solutions may not be too liquid they may be thickened with casein or caragheen extract so as to remain capable of spraying. When using hydrogen peroxide the bleaching agent is allowed to act for about a quarter of an hour to half an hour. It is then rinsed off and the skin is treated in the usual manner.

In addition to the bleaching agents already name-d use may be made for example also of sodium peroxide, sodium hydrosulphite and their equivalents.

The great value of the process according to the invention is obvious considering that genuine, marked lizard skins or leathers have double or thrice the market value of the skins or leathers of otherwise equal quality but of a uniform color. As the markings or patterns produced according to the invention on such monochrome skins or leathers resemble in every respect the genuine marking both as regards appearance and. durability the cheap monochrome skins or leathers attain a value greatly exceeding that of original skins or leathers.

It may be observed in addition that if need be any possible subsequent darkening of the bleached parts of the skin may be counteracted by the use of well known agents. This is a step which in the leather dyeing industry is frequently resorted to. I

I claim:

1. The process for the production of markings on naturally dark and inexpensive colored skins and leathers consisting in applying to the skin steeped, limed, soaked and pickled in the usual manner a bleaching agent in the condition of a pulp, to localized areas, in an amount determined by the thickness and other conditions of the pigment, allowing said bleaching agent to act on the skins and leathers at the said localized areas, removing the bleaching agent from the said areas by rinsing, so as to produce the marking and superficial appearance of relatively expensive skins and leathers.

2. The process for producing markings on naturally dark colored skins and leathers consisting in pickling a skin steeped, limed and soaked in the usual manner with about 1% sulphuric acid (0.25% concentration) and about 7% common salt calculated for the weight of the raw hide, app-lying to localized areas, a concentrated solution of bleaching powder and after allowing this bleaching agent to act for about an hour, removing it and any residue, by rinsing, so as to produce the marking and superficial appearance of relatively expensive skins and leathers.

3. The method of producing markings on naturally dark color-ed skins and leathers consisting in pickling a skin steeped, limed and soaked in the usual manner with about 1% sulphuric acid (0.25% concentration) and about '7 common salt calculated for the weight of the raw hide, treating the localized areas of the skin with potassium permanganate, exposing said localized areas of the skin to the action of said bleaching medium for 3 to 20 minutes and then immersing the skin into a solution of about 5% sodium bisulphite, and finally rinsing the skin in the usual manner so as to produce the marking and superficial appearance of relatively expensive skins and leathers.

HANS ENGELS. 

